The lumber mill industry has become largely automated. Full length tree trunks are delivered to lumber mills, where they are automatically debarked, and cut into log segments. These log segments are then typically processed at a number of automated stations, depending on the lumber mill and the type of wood. These processing stations produce lumber from each log segment. The resulting lumber is generally intended for use as building construction material, but is often used in any of a wide variety of applications, such as non-building construction, furniture, and decorative objects.
In general, the tree trunks that are delivered to saw mills typically have a high level of moisture content. As such, the resulting lumber is referred to as green lumber. Green lumber is usually dried or otherwise treated to reduce the moisture content level to produce lumber with improved strength, durability, and other attributes. Green logs or lumber can be dried, for example, by simply allowing the cut wood to sit in dry air for weeks or months, but most modern large-scale lumber production includes controlled drying of cut green lumber pieces in a kiln.
Lumber is often sold by size, and not fully differentiated by the species of the tree from which it was cut. For example, a Canadian softwood lumber product not fully differentiated by species is SPF, which includes a combination of spruce, pine, and fir. SPF from Eastern Canada may include, for example, red spruce, black spruce, jack pine, and balsam fir species. SPF from Western Canada may include, for example, white spruce, Engelmann spruce, lodgepole pine, and alpine fir.